250 THE HISTORY OF CREATION. 
There appears indeed to be a limit given to the adapt- 
ability of every organism, by the “type” of its tribe or 
phylum; that is, by the essential fundamental qualities 
of this tribe, which have been inherited from a common 
ancestor, and transmitted by conservative inheritance to all 
its descendants. Thus, for example, no vertebrate animal 
can acquire the ventral nerve-chord of articulate animals, 
instead of the characteristic spinal marrow of the vertebrate 
animals. However, within this hereditary primary form, 
within this inalienable type, the degree of adaptability is 
unlimited. The elasticity and fluidity of the organic 
form manifests itself, within the type, freely in all directions, 
and to an unlimited extent. But there are some animals, 
as, for example, the parasitically degenerate crabs and 
worms, which seem to pass even the limit of type, and 
have forfeited all the essential characteristics of their tribe 
by an astonishing degree of degeneration. As to the 
adaptability of man, itis, as in all other animals, also un- 
limited, and since it is manifested in him above all other 
animals, in the modifications of the brain, there can be 
absolutely no limit to the knowledge which man in a 
further progress of mental cultivation may not be able to 
exceed. The human mind, according to the law of unlimited 
adaptation, enjoys an infinite perspective of becoming ever 
more and more perfect. 
These remarks are sufficient to show the extent of the 
phenomena of Adaptation, and the great importance to 
be attached to them. The laws of Adaptation, or the 
facts of Variation caused by the influence of external con- 
ditions, are just as important as the laws of Inheritance. 
All phenomena of Adaptation, in the end, can be traced to 
